Seal coating, also called abradable coating, was mainly applied in fan, compressor and turbine of aircraft engine to protect rotating component and meanwhile reduce the clearance and improve the efficiency.

Yet due to the harsh working conditions such as super high sliding speed and environment temperature and intermittent contact form, the tribological behavior between seal coating and counterpart blade have not been symmetrically studied and the wear mechanism was not fully understood. The seal coating damaged the blade or adhered to the blade, which could bring disastrous consequences to the engine during service.

Recently the adhesion mechanism of Al-hBN coating to TC4 blade was investigated by Prof. DUAN Deli, Dr. GAO Siyang and Dr. XUE Weihai from Specialized Materials and Devices Division, Institute of Metal Research, Chinese Academy of Sciences. The adhesion was found to be closely related to working condition. The combination of low incursion per strike and high rubbing speed resulted in the most serious adhesion.

By comparing the adhesive layer on the blade tip with the original coating, the fierce friction-induced heat under high sliding speed was found to be the key factor that made the metal phase Al melted and transferred to the blade tip during blade rubbing process.

Tribological behavior of CuAl-NiCg coating and GH4169 blade was further studied and shear lip phenomenon occurred in real service condition of the aircraft engine have been reproduced. The volume of shear lip was the maximum and the blade wear degree was the highest under the condition with high sliding speed and low incursion rate.

Based on the summary of wear mechanisms of different sealing couples, the effect of the friction heat on the tribological behaviors of the seal coatings and blades was identified particularly.

Therefore, the one-dimensional heat conduction model was established to discover the important influence of thermal properties of sealing couples on the temperature raising rate of contact area, which brought about different tribological behavior of the coating adhering to the blade or damaging the blade.

Those findings were published in Wear recently.

Contact
HUANG Chengyu
Institute of Metal Research, Chinese Academy of Sciences
tel: + 86 (24) 23971608
E-mail:cyhuang@imr.ac.cn